Diagnostic device for a field bus with control-independent transfer of information

ABSTRACT

A diagnostic device that may be included in a superior-level application, for example as an ActiveX component with a software interface standardized for this purpose. The superior-level application may be a visualization application of a control application or a visualization at the control level. The diagnostic device receives diagnostic data for a field bus from a field bus switching component. The diagnostic data is transmitted via a PLC I/O bus and interfaces provided in the PLC, without the need to parameterize or program either the control application or the visualization application.

DESCRIPTION

[0001] The invention relates to a diagnostic device for a field bus which outputs diagnostic information and parameters, as well as certain information about peripheral properties, to a display instrument for display and evaluation.

[0002] State of the Art

[0003] As the use of field bus systems in control systems becomes more and more widespread, the importance of tools for the rational commissioning and maintenance of such field bus systems is constantly growing also. A diagnostic device for a field bus is known from the technical article published in “Elektronik Praxis, issue 23, pp.108-110”. The diagnostic device described therein fulfils the object of providing diagnostic data for a field bus in the form of a clear text message or a visual display, as a histogram for example, for long-term analyses. In terms of content, the display provides visual identification of fault locations in the event of sporadic transmission errors, monitoring of quality in fibre optic lines and messages from bus modules regarding faults on associated peripherals. However, the critical disadvantage of this device is that the logical and physical connection between the field bus switching component and the diagnostic device is assured via a purpose-designed interface connection between the field bus switching component and the computer with diagnostic device, such as Ethernet or V24.

[0004] A visualisation system is known from DE 299 13 057 U1, in which the logical and physical connection between the programmable logic controller PLC and a visualisation application is assured by an interface provided for that purpose (for example V24 or Ethernet). For additional field bus switching components connected to the PLC, the interface that is located in the field bus switch must be used to transmit the diagnostic data contained in the field bus switch, it is not possible for the diagnostic information contained in the PLC to be transferred to the diagnostic device.

[0005] The standardised software interface for ActiveX components is known from “Inside OLE Second Edition, Kraig Brockschmidt, Microsoft Press, 1985” and “ActiveX Controls Inside Out, Adam Denning, Microsoft Press, 1987”.

[0006] “Elektro Automation, 3/2001, Page 32”, includes a description and illustration of the typical data communication mechanism for a diagnostic device for a field bus. In this case, programming effort is required within the control unit in order to transfer the data in the control unit to a diagnostic device. To avoid costly programming activities, the diagnostic device is integrated in a visualisation application as an ActiveX software component. Since the transmission path of the diagnostic data from the field bus to the diagnostic devices no longer passes through the controller, and additional interface connection is required therefor.

[0007] A diagnostic device in a process controlling system is known from DE 100 08 020 A1. In this case, however, only measurement and control variables from the application are monitored, and a fault is output to the display or action is initiated. The diagnostic device in DE 100 08 020 A1 is a constituent part of the control device, since the performance of the control program is influenced by the diagnostic device. The diagnostic device described here has the critical disadvantage that it does not monitor the functioning of a field bus or process control network.

OBJECT OF THE INVENTION

[0008] The object of the invention is to provide a diagnostic device that may be included in a superior-level application, for example as an ActiveX component with the standardised software interface. The superior-level application may be a visualisation of the control application or a visualisation at the control level. The diagnostic device receives the diagnostic data for the field bus from the field bus switching component. The diagnostic data is transmitted via the PLC I/O bus and the interface provided in the PLC. Both the control application and the visualisation application are unaffected by the transmission of the diagnostic data for the field bus and need not be considered for purposes of programming or use. Since no additional interface connection is provided for transmitting diagnostic data between the field bus switching component and the diagnostic device, the internal PLC I/O bus, the external interface for the PLC, and the external interface in the computer are used.

[0009] Solution to the Object

[0010] The object is solved according to the invention by the features described in claim 1. The diagnostic device for a field bus according to the invention is a software component that is integrated in a superior-level application via a standardised standardised software interface and is run via that interface. The diagnostic device preferably has the form of an ActiveX component with the standardised software interface provided therefor. The term ActiveX component is used to a describe a software component that may be integrated in a main application via a standardised software interface to the main application. The ActiveX component is attached to the main application before the main application is launched or during runtime thereof.

[0011] The interface on the computer has the task of communicating the diagnostic data from the external interface of the computer to the diagnostic device within the computer. In the PLC, the diagnostic data is transmitted from the field bus switching component to the external interface of the PLC via the interface in the PLC. No modifications or programming changes need to be made to the control application in the PLC in order for the diagnostic device to function. No modifications or programming changes need to be made to the visualisation application on the computer to enable the transfer of the diagnostic data that the diagnostic device needs in order to function.

[0012] The invention will be described in the following with reference to an exemplary embodiment and the associated figures.

[0013] Key to Parts

[0014]1: Programmable logic controller PLC

[0015]2: Interface in the PLC

[0016]3: Control application, PLC program

[0017]4: Field bus switching component, central unit for the field bus system

[0018]5: I/O units, input or output units for the PLC

[0019]6: PLC I/O bus, internal bus of the PLC or PLC extension bus

[0020]7: External interface of the PLC

[0021]8: Logical I/O interface of the bus connecting circuit to the PLC I/O bus

[0022]9: External interface of the bus connecting circuit

[0023]10: Display device, computer for control-specific visualisation application

[0024]11: Diagnostic device for a field bus

[0025]12: Interface in the computer

[0026]13: Visualisation application, software component

[0027]14: Diagnostic data for a field bus, transmitted via the PLC I/O bus

[0028]15: Logical connection between the computer interface and the diagnostic device for a field bus, inside the computer

[0029]16: Logical connection between control application and the external interface of the PLC, inside the PLC

[0030]17: External interface of the computer

[0031]18: Data link between PLC and computer

[0032]19: Link for diagnostic data for a field bus

[0033]20: Data link between PLC and computer

[0034]21: Field bus circuit (schematic)

[0035]22: Field bus node, for connecting multiple slave bus modules

[0036]23: Bus modules, contain inputs and outputs for the

[0037] control application

[0038]24: Fault point in the field bus

[0039]25: Bus module

[0040]26: Bus module downstream of the fault point

[0041]27: Field bus

[0042]28: Software interface for ActiveX component

HEADINGS OF FIGURES

[0043]FIG. 1: shows the diagnostic device for a field bus according to the invention, which receives the diagnostic information via the external interface located in the PLC.

[0044]FIG. 2: shows an example of a field bus layout.

[0045]FIG. 3: shows a diagnostic device for a field bus such as is already known in the art.

EXEMPLARY EMBODIMENT

[0046]FIG. 1 shows the arrangement according to the invention with a diagnostic device 11 for a field bus. The diagnostic data specific to the field bus is stored in field bus switching component 4 prior to further processing in diagnostic device 11. Field bus switching component 4 with its I/O interface 8 is coupled to PLC I/O bus 6 located in PLC SPS 1, so that field bus switching component 4 may be addressed in the same way as I/O units 5 by control application 3. Frequently, a display device 10 is connected to PLC 1, and contains a visualisation application 13 associated with control application 3. All essential information is carried over data link 18 between the external interface of PLC 7 and the external interface of computer 17. Diagnostic device 11 is activated as an additional component in display device 10, which collects diagnostic data about the field bus for further processing or visual display. To enable transmission of the diagnostic data from field bus switching component 4 to diagnostic device 11 without the need to modify or program the control application or the visualisation application, interfaces 2, 12 handle the corresponding data allocation. The diagnostic device is operated from the visualisation application via software interface 28, feedback signals from diagnostic device 11 also pass through this software interface 28 to visualisation application 10.

[0047] In the following, the transmission of diagnostic information from field bus switching component 4 to diagnostic device 11 is described. The diagnostic information concerning the field bus that is stored in field bus switching component 4 is transferred to the interface in PLC 2 via PLC I/O bus 6. Link 14 for the diagnostic information field bus switching component 4 and PLC I/O bus 6 is adapted to match PLC I/O bus 6 and may also be purely logical in nature. Both I/O data and diagnostic information for the field bus is transmitted via PLC I/O bus 6 to the interface in the PLC 2. The interface in PLC 2 switches the logical connections. The diagnostic information is routed to the external interface of the PLC 7. The I/O data is routed to the control application 3 via the internal logical link 25. Visualisation information from control application 3 reaches the interface of the PLC 2 via internal logical link 16, and is forwarded from that interface to the external interface 7 of PLC 1. External interface 7 of the PLC 1 may be a V24 interface or an Ethernet interface, or a an interface for a different transmission mode, such as parallel transmission.

[0048] The visualisation information and diagnostic information for the field bus is received in display device 10 with visualisation application 13 via external interface 17 in computer 10. Interface 12 in computer 10 routes the received information either to visualisation application 13 or to diagnostic device 11 depending on its allocation. Visualisation information is routed to visualisation application 13, diagnostic information is routed to diagnostic device 11 via the internal logical channel 15. The functional property of visualisation application 13 is not affected thereby. Switching of all logical links can also be done in the reverse direction, so that commands and parameters originating from diagnostic device 11 and destined for field bus switching component 4 can be transmitted via data link 18 and PLC I/O bus 6. Parameters or programs for control application 3 can be transmitted to PLC 1 via data link 18 from visualisation application 13. Of course application 13 on the computer may also be a programming application for the PLC or a configuration or programming application for the field bus. Interface 12 in computer 10 may take the form of a programmable data processing unit or a component arranged as a hardware device.

[0049]FIG. 2 shows an exemplary configuration in which a field bus 27 is connected to field bus switching component 4. This may be, for example, an INTERBUS system, but may equally be a different field bus system. Typically, field bus 27 includes bus circuits 21 and modules 23, 25, 26, connected thereto, which are furnished with peripheral wiring to serve as connections for sensors or actuators or other instruments associated with automation technology.

[0050] A bus terminal 22 is shown for purposes of illustrating the INTERBUS system only, to demonstrate coupling of multiple bus modules 23 into a functional grouping. A fault 24 on the connection circuit upstream of module 26 generates an error that is stored in field bus switching component 4 together with as much information as possible (type, duration, location of fault, etc.).

[0051]FIG. 3 shows a diagnostic tool 21 designed according to the known art for receive diagnostic information. A physical connection 19 provided specifically for this purpose transports the diagnostic information to diagnostic device 11. In the reverse direction, commands and parameters for running the bus may be sent from diagnostic device 11 to field bus switching component 4. PLC I/O bus 6 contains only I/O data, so that control application 3 can receive this data directly. Data link 20 between interfaces 7 and 17 carries only visualisation information or other control-related data from control application 3, and in the other direction it carries only control related parameters or programs from visualisation application 13 destined for control application 3. 

1. A diagnostic device (11) for a field bus (27), which outputs for display at a display device (10) field bus-related information such as nonrecurring transmission errors, persistent signal loss with location information, line quality of fibre optic lines, and other diagnostic information of significance for the field bus, characterized in that the diagnostic information is routed by the field bus switching component (4) via the internal bus (6) of the PLC or PLC extension bus (6) to the external interface (7) of PLC (1), without affecting the control application (3).
 2. The diagnostic device according to claim 1, characterized in that the control application (3) does not require any of the programming activities that are associated with the diagnostic device (11) in the programming phase.
 3. The diagnostic device according to claim 1 or 2, characterized in that the transfer of diagnostic information within the PLC (1) is performed by the interface (2) of the PLC (1), which consists of a software programmable data processing unit.
 4. The diagnostic device according to claim 1 or 2, characterized in that the transfer of diagnostic information within the PLC (1) is performed by the interface (2) of the PLC (1), which consists of a hardware component designed specifically for this purpose.
 5. The diagnostic device according to any of the preceding claims, characterized in that an interface (12) on display device (10) handles the logical distribution of the information to be transmitted, wherein the diagnostic information is communicated to the diagnostic device (11) and the information destined for the visualisation or programming application is communicated to the visualisation or the programming application (13).
 6. The diagnostic device according claim 5, characterized in that the diagnostic device (11) is integrated as an Active-X component into an existing application (13) on the display device (10).
 7. The diagnostic device according claim 5 or 6, characterized in that the diagnostic device (11) receives the diagnostic information from the visualisation application via a standardised interface for ActiveX components.
 8. The diagnostic device according claim 5 or 6, characterized in that the existing application (13) on the display device (10) is a visualisation application (13).
 9. The diagnostic device according claim 5 or 6, characterized in that the existing application (13) on the display device (10) is a programming application for the PLC (1).
 10. The diagnostic device according claim 5 or 6, characterized in that the existing application (13) on the display device (10) is a configuration application or programming application for the field bus (27). 